1. Field of the Invention
The present invention relates to an angle detection device for detecting an inclination angle of an object to be measured with respect to a horizontal plane. The present invention also relates to an image reading apparatus with the angle detection device incorporated therein.
2. Description of the Related Art
Conventionally, image reading apparatuses that pick up an image of a sheet-like medium while conveying the medium have been proposed. In such an image reading apparatus, when a sheet-like medium is inserted in an apparatus body, the medium is conveyed to an imaging device by a conveying roller, imaged by an imaging device, and is ejected from the apparatus body by the conveying roller.
In addition, for example, if the image reading apparatus is compact in size, the apparatus body may be installed in a wall-mounted state or a stationary state. That is, the apparatus body is sometimes installed in an inclined state with respect to the horizontal plane.
As a technology related to the installation of the apparatus body in the inclined state with respect to the horizontal plane, there is proposed an invention in which an installation state of a printer is detected by a posture detection unit and torque of a step motor used for feeding roll paper is controlled according to whether the printer is used in a stationary installation or in a wall-mounted installation (Japanese Patent Application Laid-open No. 2000-72296).
The printer disclosed in Japanese Patent Application Laid-open No. 2000-72296 detects an installation state of the printer by the posture detection unit, and increases the torque of the step motor, if the printer is used in the wall-mounted installation, by reducing a feeding speed of the roll paper as compared with the case where the printer is installed in the stationary state. In other words, the printer in Japanese Patent Application Laid-open No. 2000-72296 detects the installation state of the printer by the posture detection unit, and generates the torque sufficient for feeding the roll paper by reducing the feeding speed of the roll paper, in the case of the installation state such as the wall-mounted installation in which the pull-out load of the roll paper is comparatively high, as compared with the case of the installation state such as the stationary installation in which the pull-out load of the roll paper is comparatively low.
Angle detection devices are generally used to detect an inclination angle of an object to be measured with respect to the horizontal plane. Such an angle detection device includes a rotary encoder or a conventionally known angle sensor such as an angular velocity sensor, but a sensor with a new configuration is desired.